On Fri, 6 Oct 2023 10:12:53 GMT, Quan Anh Mai <qa...@openjdk.org> wrote:
>> @merykitty For a `String` input that would mean copying the suffix, which
>> could be quite long, or make use of the method that accepts a
>> `CharSequence`, which has different (although more complete) exception
>> messages. Perhaps in a followup PR.
>>
>> What would be _really_ nice is to be able to write, for example (leaving
>> apart the exception messages issue above)
>>
>> public static int parseInt(String s, int radix)
>> throws NumberFormatException {
>> return parseInt(s, 0, s.length(), radix); // delegate to the
>> CharSequence method
>> }
>>
>> and leave it to the runtime compiler to perform something similar to
>> * make a copy of the `parseInt(CharSequence,int,int,int)` code into
>> `parseInt(String,int)`
>> * adapt the copy to the `String` case by replacing `invokeinterface` for
>> `charAt()` with `invokevirtual`, which can be further optimized to direct
>> invocation because `String` is final, and eventually inlined perfectly.
>>
>> Currently, that does not seem to happen, but I might be wrong.
>> This would spare us 4 code duplications here, and perhaps in many other
>> places where we have almost identical methods for `String` and
>> `CharSequence`.
>
> @rgiulietti We can do the same thing as the Vector API does, that is to have
> a private `parseInt(CharSequence, int, int, int)` that is annotated with
> `@ForceInline`. When called from `parseInt(String, int)`, the compiler, after
> inlining the former method, can devirtualise all calls to `charAt`, etc. This
> is like a poor man workaround for monomorphism.
>
> @ForceInline
> private int parseUnsignedInt(CharSequence, int, int, int) {}
>
> public int parseUnsignedInt(String s, int radix) {
> return parseUnsignedInt(s, 0, s.length(), radix); // After inlining,
> this call behaves as if it is a parseUnsignedInt(String, int, int, int)
> }
>
> Thanks.
@merykitty Interesting. I'll prepare a followup PR in the near future.
>> Oops @merykitty, I see right now that `compareUnsigned` is an intrinsic, so
>> I'll give it a try.
>
> It's not really about performance, I just think that it is more readable the
> other way.
Well, two lines above the usage there's a comment that should help the reader...
-------------
PR Comment: https://git.openjdk.org/jdk/pull/16050#issuecomment-1750348693
PR Review Comment: https://git.openjdk.org/jdk/pull/16050#discussion_r1348523537
